The intention lies in the field of manufacturing integrated optical components. More in particular, it relates to a method for manufacturing branching-off or intersecting channel-shaped waveguides on or in a substrate, which substrate encloses a light-guiding layer, and on which substrate there is applied an auxiliary-mask layer, which method comprises the following steps:
a first application step for applying a first mask pattern of a first mask material in a first mask position on the auxiliary-mask layer, which first mask pattern comprises a subpattern for the definition of a first channel-shaped waveguide,
a first etching step for etching portions of the auxiliary-mask layer not covered by the first mask pattern with the help of first etchants,
a removal step for removing the first mask material of the first mask pattern, with an auxiliary-mask pattern of auxiliary-mask material remaining on the substrate,
a second application step for applying a second mask pattern of a second mask material in a second mask position which overlaps the position of the auxiliary-mask pattern at least in part, which second mask pattern comprises a subpattern for the definition of a second channel-shaped waveguide which makes an acute angle with the first waveguide,
a second etching step for etching portions of the substrate not covered by mask material with the help of second etchants,
an intermediate etching step carried out between the first and the second etching step with the help of third etchants.
Such a method is disclosed in the European patent specification EP-A-0599394. In this known method, there is, first realized a composite mask pattern which consists of an auxiliary-mask pattern formed by the first mask pattern transferred to the auxiliary-mask material of the auxiliary-mask layer, and a second mask pattern of photosensitive mask material overlapping the auxiliary-mask pattern. Said composite mask pattern is then used in the second etching step, the actual etching step for etching the substrate. Said known method has the restriction that for a good result it is required that the materials of the auxiliary-mask layer and of the second mask pattern be sufficiently resistant to the etchants used in the second etching step. Such is not always feasible in practice. Thus, it has become apparent that an accepted photosensitive mask material, such as photoresist, is not sufficiently resistant under a dry-etching step, such as, e.g., with an oxygen plasm, with which the substrate of a semiconductor material, such as InP, is etched.